Solutions of polyester-imides

ABSTRACT

Polyester-imide resins are prepared which are soluble in non-phenolic solvents by incorporating a monoether of a diethylene glycol or triethylene glycol into the resin.

This is a division of application Ser. No. 770,310 filed Feb. 22, 1977.

It is known to make polyester and polyester-imide wire enamels in whichthe polymer is soluble in a solvent comprising a large amount of aphenolic solvent, e.g., phenol, cresol or cresylic acid. Thus, seeWeddleton U.S. Pat. No. 3,853,817, Schmidt U.S. Pat. No. 3,852,246,Meyer U.S. Pat. No. 3,426,098, Schmidt U.S. Pat. No. 3,562,219, SattlerU.S. Pat. No. 3,668,175, Schmidt U.S. Pat. No. 3,697,471, Schmidt U.S.Pat. No. 3,793,250, Schmidt U.S. Pat. No. 3,839,264 and Schmidt U.S.Pat. No. 3,929,714. The use of phenolic solvents is disadvantageousbecause of their relatively high toxicity and objectionable odor and theconsequent problems in recovering them after application of the enamelto the wire. In Weddleton and Meyer there is mentioned the use ofN-methyl pyrrolidone as a solvent. This solvent also is objectionable tosome extent because of its noxious odor.

It has been proposed in Ito Japanese published application 49-59478 toprepare polyester resins of low molecular weight and then dissolve themin monoalkyl ethers of diethylene glycol and triethylene glycol to makewire enamels. Similarly in Okada Japanese published application 51-16342it has been proposed to prepare polyester resins of low molecular weightand then dissolve them in monoalkyl ethers of mono, di or triethyleneglycol or mono, di or tripropylene glycol. Neither Ito nor Okadaattempted to react the monoalkyl ether of the polyalkylene glycol informing the polyester nor in preparing products from polyester-imides.As the monoalkyl ether of the polyalkylene glycol can act as amonofunctional alcohol it can be seen that to add it prior to formationof the polyester would result in a modification of the product formedwith attendant unpredictable properties.

Also it is known that polyester-imides have different properties thanpolyesters. Thus, when a low molecular weight polyester-imide is made ina manner somewhat analogous to that of the aforementioned Ito and Okadapublished Japanese applications, the product is not readily soluble inthe monomethyl ethyl of diethylene glycol (Methyl Carbitol) alone, butis soluble in a mixture of Methyl Carbitol and N-methyl pyrrolidone. Italso has been found that the monoethyl ether of diethylene glycol andthe monobutyl ether of diethylene glycol do not act as solvents forpolyester-imides, another difference from the reported results withpolyesters.

It has now been found that novel polyester-imides can be prepared whichare soluble in non-toxic solvents such as Methyl Carbitol if during theformation of the polyester imide there is employed as a reactant eitheran ether of the formula:

    RO(C.sub.n H.sub.2n O).sub.x H

where R is an alkyl group of 1 to 6 carbon atoms or phenyl, n is 2 or 3and x is 2 or 3 or the monophenyl ether of ethylene glycol or mixturesof such monoethers. Examples of such monoethers where R is as definedabove are monomethyl ether of diethylene glycol, monomethyl ether oftriethylene glycol, monomethyl ether of dipropylene glycol, monomethylether of tripropylene glycol, monoethyl ether of diethylene glycol,monoethyl ether of triethylene glycol, monoethyl ether of dipropyleneglycol, monoethyl ether of tripropylene glycol, monoisopropyl ether ofdiethylene glycol, monoisopropyl ether of triethylene glycol,monoisopropyl ether of dipropylene glycol, monoisopropyl ether oftripropylene glycol, monopropyl ether of diethylene glycol, monobutylether of diethylene glycol, monobutyl ether of triethylene glycol,monobutyl ether of dipropylene glycol, monobutyl ether of tripropyleneglycol, monohexyl ether of diethylene glycol, monohexyl ether oftriethylene glycol, monohexyl ether of dipropylene glycol, monophenylether of diethylene glycol, monophenyl ether of tripropylene glycol.More preferably R is alkyl of 1 to 4 carbon atoms, most preferablymethyl or ethyl. The presently preferred compound is the monomethylether of diethylene glycol.

The parameters of the development are as follows:

1. A polyester-imide made with a hydroxy to carboxyl ratio of 1.25:1 to2:1, preferably 1.8:1 to 2:1.

2. Polyester to polyimide groups within the conventional range, e.g., 95to 50% by weight polyester groups and 5 to 50% by weight polyimidegroups, preferably 85 to 65% polyester groups and 15 to 35% polyimidegroups.

3. The polyester-imide is made with 5 to 40% or even up to 45% of thehydroxyl groups being present as the glycol monoether of the type setforth above, more usually 5 to 30%, and more preferably 5 to 20% of thehydroxyl groups being present as the glycol monoether, most preferably 5to 12% being present as the glycol monoether.

4. While the modified polyester-imides of the present invention aresoluble in a wide variety of solvents including phenols, e.g., phenolper se, cresol or cresylic acid, they are preferably dissolved in asolvent containing 40% to 100% of diethylene glycol monoalkyl or phenylether or triethylene glycol monoalkyl or phenyl ether of the type setforth above, most preferably 50 to 100% of such monoalkyl ether of adiethylene glycol. When a cosolvent is used it can be, for example,N-methyl pyrrolidone or aliphatic hydrocarbons, e.g., octane, decane,dodecane, but more preferably is an aromatic hydrocarbon such asbenzene, toluene, xylene, monoalkyl benzenes boiling in the range315°-350° F. (Solvesso 100), a mixture of tetramethyl benzene withdialkyl and trialkyl benzenes boiling in the range 360°-400° F.(Solvesso 150), a blend of 70% Solvesso 150 with 30% heavy aromaticnaphtha (the blend being known as Solvesso N-150), or the like. Thesolvent can be 100% monoalkyl or phenyl ether of diethylene glycol ortriethylene glycol, or the phenyl ether of ethylene glycol. Also therecan be used the monophenyl ether of ethylene glycol, alone or incombination with a monoalkyl or phenyl ether of diethylene glycol ortriethylene glycol. Preferably the solvent is essentially free ofphenolic solvents.

5. The monoether modified polyester-imide normally has an averagemolecular weight of from 500 to 1500, e.g., 500 to 1200, usually 550 to1200, prior to being dissolved in the solvent. The modifiedpolyester-imide is of sufficiently low molecular weight that it can bedissolved in a mono lower alkyl ether of diethylene glycol or in thephenyl ether of either diethylene glycol or ethylene glycol.

6. The polyester-imide is made using (1) a trifunctional polyol such astris(2-hydroxyethyl)isocyanurate (THEIC), glycerine, trimethylolethaneor trimethylol propane, (2) a dibasic acid such as isophthalic acid,terephthalic acid or benzophenone dicarboxylic acid or their lower alkylesters, e.g., dimethyl terephthalate dimethyl isophthalate or dibutylterephthalate, (3) trimellitic anhydride (TMA), (4) a diamine,preferably an aromatic diamine, e.g., methylene dianiline, oxydianiline,2,4-tolylene diamine, 2,6-tolylene diamine, benzidine,3,3'-diaminodiphenyl, 1,4-diaminonaphthalene, p-phenylene diamine,α'ω-nonamethylene diamine, 4,4'-diaminodiphenyl ether, 4,4-dimethylheptamethylene diamine-1,7, diaminodiphenyl ketone,bis-(4-aminophenyl)-α,α'-p-xylene, m-phenylene diamine, xylene diamine,hexamethylene diamine, ethylene diamine, 4,4'-dicyclohexylmethanediamine or diaminodiphenyl sulfone. The preferred diamines are firstmethylene dianiline and second oxydianiline or tolylene diamine.Optionally there can be present a dihydric alcohol such as ethyleneglycol, neopentyl glycol, butanediol-1,4, butanediol-1,3,1,4-cyclohexanedimethanol, 2,2,4-trimethyl-1,3-pentenediol, propylene glycol,diethylene glycol, trimethylene glycol, hexanediol-1,6 and dipropyleneglycol. Up to 10 molar % of the aromatic dicarboxylic acid can bereplaced by an aliphatic dicarboxylic acid such as adipic acid, sebacicacid, azelaic acid or the like. The preferred trihydric alcohol isTHEIC, the preferred aromatic dibasic acid is terephthalic acid.

7. The amount of THEIC or other trihydric alcohol component is at least20% or more preferably 30% of the total alcohol on an equivalent basisand it and the glycol monoether together can be 100% of all of thealcohol component although usually there is present some dihydricalcohol, e.g., in an amount of at least 10% of the total weight of thealcohols.

The hydroxyl number of polyester imides frequently is within the rangeof 180 to 270, but this can be varied, e.g., it can be as low as 150 oras high as 350 or 400.

The acid number of the products is usually below 6.

The use of the monoether of a glycol as a reactant which serves as amonofunctional alcohol serves to control the molecular weight andsolubility of the polymer and permits the manufacture of wire enamelswhich contain relatively non-toxic solvents in place of phenols and alsopermits the attainment of enamels having economical high solidscontents.

Thus, the modified polyester-imide resins of the invention can bedissolved in 100% methyl Carbitol or 100% monomethyl ether oftriethylene glycol, or 100% butyl Carbitol, or a mixture of themonophenyl ether of ethylene glycol and the monophenyl ether ofdiethylene glycol or a mixture of methyl Carbitol with the ethyl etherof diethylene glycol (Carbitol) to give enamels having a solidsconcentration of 30 to 70%, preferably 45 to 55%. As indicated abovearomatic hydrocarbon diluents can be added. The diluents do not increasethe solubility but reduce the overall cost of the solvent.

There can be added to the wire enamels of the invention conventionalmodifiers such as titanates, such as tetraisopropyl titanate, tetrabutyltitanate, tetraphenyl titanate, dibutyl triethanolamine titanate,tetrahexyl titanate, tetramethyl titanate, etc., as well aspolyisocyanates, e.g., Mondur SH which is the cyclic trimer of 2,4 and2,6-tolylene diisocyanates having the three free isocyanate groupsblocked by cresol and the other polyisocyanates mentioned in the Meyerpatent set forth above, or metal driers, e.g., cobalt naphthenate, zincresinate, zinc octoate, cadmium linoleate, zinc naphthenate. Also therecan be added to the enamel resins such as melamine-formaldehyde resin orphenolic resins such as phenol-formaldehyde, cresol-formaldehyde andxylenol-formaldehyde resins.

The wire enamels can be applied to copper, silver, aluminum or otherwires using conventional coating procedures and wire speeds and curingthe wire is carried out at conventional temperatures, e.g., 500° to 900°F., usually 500° to 800° F.

The composition can comprise, consist essentially of or consist of thematerials set forth.

Unless otherwise indicated all parts and percentages are by weight.

The following abbreviations are used in the examples:

    ______________________________________                                        TA         =       terephthalic acid                                          DMT        =       dimethyl terephthalate                                     TMA        =       trimellitic anhydride                                      THEIC      =       tris(hydroxyethyl)isocyanurate                             NMP        =       N-methyl pyrrolidone                                       MDA        =       4,4'-methylene dianiline                                   TPT        =       tetraisopropyl titanate                                    ______________________________________                                    

EXAMPLE 1

    ______________________________________                                                       Grams                                                          ______________________________________                                        1. methyl Carbitol                                                                             472                                                          2. ethylene glycol                                                                             218                                                          3. THEIC         850                                                          4. TMA           548                                                          5. MDA           282                                                          6. TA            312                                                          7. TA            312                                                          ______________________________________                                    

Parts 1 through 4 were charged to a 5-liter flask equipped with anagitator, a thermometer and an air-cooled Snyder column connected to adistillation receiver. The temperature was increased to 230° F., parts 5and 6 were added. The temperature was allowed to increase to 392° F.When 67 cc of distillate were collected, part 7 was loaded into theflask. The temperature was allowed to increase to 446° F. and aftercollecting 320 cc of distillate a sample of resin was withdrawn from theflask. The viscosity was found to be M 1/2 (Gardner-Holdt) measured at30% solids in cresylic acid. 20 inches of vacuum was then applied to theflask with a gradual increase to 24 inches. Upon removing 100 cc ofdistillate under vacuum, the reaction product was discharged from theflask. The viscosity of the finished polymer was N 1/2 (G-H) measured at30% solids in cresylic acid. In methyl Carbitol the viscosity was C 1/2at 40% solids. The viscosity of the solid resin was 460 cps at 365° F.when measured with a Brookfield viscometer.

The molecular weight as determined with a vapor phase osmometer was 571and the hydroxyl value was 155.

The modified polyester-imide formed was dissolved in a mixture of methylCarbitol and water. 10.2 parts of the ester imide dissolved in 10.2parts of an 80/20 (by volume) mixture of methyl Carbitol/water. Theviscosity was a U and the solids were 44.9%. No adjustment in the pH ofthe system was needed nor were amine solubilizers necessary.

EXAMPLE 2

    ______________________________________                                                             Grams                                                    ______________________________________                                        1.     The methyl Carbitol modified                                                  polyester-imide prepared in                                                   Example 1           480                                                2.     Cresylic Acid       178                                                3.     Solvesso 100        158                                                4.     C. P. Phenol        115                                                5.     Cresylic Acid       30                                                 6.     Solvesso 100        80                                                 7.     C. P. Phenol        94                                                 8.     X03-02 (Mondur SH dissolved                                                   in Cresylic Acid -                                                            Solvesso 100)       106                                                9.     P11-13 (m,p-cresol-formaldehyde                                               resin dissolved in Cresylic                                                   Acid - Solvesso 100)                                                                              48                                                 10.    TPT                 17                                                 11.    Cresylic Acid       17                                                 ______________________________________                                    

A solution of the polymer prepared in Example 1 was made by dissolvingthe resin in 2,3,4 and holding the mixture at 250° F. with agitationuntil it was dissolved. The solution was further diluted with 5,6 and 7whereupon 8 and 9 were added. Ten and 11 were premixed and then added tothe wire enamel mix. The mix was then heated to 250° F. and held for 2hours. The viscosity of the resulting wire enamel was a P and the solidswere determined to be 37.2%.

EXAMPLE 3

    ______________________________________                                                            Grams                                                     ______________________________________                                        1.     The methyl Carbitol modified                                                  polyester-imide prepared in                                                   Example 1          750                                                 2.     Methyl Carbitol    240                                                 3.     Solvesso N-150     240                                                 4.     Mondur SH          63.6                                                5.     Methyl Carbitol    95.4                                                6.     TPT                17                                                  7.     Cresylic Acid      17                                                  8.     N-methyl pyrrolidone                                                                             60                                                  ______________________________________                                    

The polyester-imide resin made in Example 1 was dissolved in a solventsystem consisting primarily of methyl Carbitol and Solvesso N-150 as canbe seen from the above-formulation.

The resin was dissolved in 2 and 3 at 250° F. with agitation. Part 4 waspredissolved in 5 and the TPT was stabilized with an equal amount ofcresylic acid and then added. The solution was heated to 250° F. andmaintained with agitation for two hours whereupon part 8 was added. Theresulting wire enamel had a viscosity of Y 1/2 (G-H) at 49% solids.

EXAMPLE 4

    ______________________________________                                                            Grams                                                     ______________________________________                                        1.     The methyl Carbitol modified                                                  polyester-imide prepared in                                                   Example 1          375                                                 2.     Methyl Carbitol    120                                                 3.     Solvesso 150       120                                                 4.     Mondur SH          35                                                  5.     Methyl Carbitol    52.5                                                6.     TPT                10                                                  7.     Cresylic Acid      10                                                  8.     NMP                15                                                  ______________________________________                                    

A wire enamel coating solution was made using the above-formulation andthe procedure as in Example 3. The viscosity of the resulting solutionwas an X (Gardner-Holdt) at 49.4% solids.

EXAMPLE 5

    ______________________________________                                                            Grams                                                     ______________________________________                                        1.     The methyl Carbitol modified                                                  polyester-imide prepared in                                                   Example 1          750                                                 2.     Methyl Carbitol    240                                                 3.     Ethyl Alcohol      240                                                 4.     Mondur SH          70                                                  5.     Methyl Carbitol    105                                                 6.     TPT                17                                                  7.     Cresylic Acid      17                                                  8.     Ethylene Glycol    30                                                  9.     N-Methyl Pyrrolidone                                                                             30                                                  ______________________________________                                    

The polyester-imide made in Example 1 was dissolved in a solventcomprised primarily of ethyl alcohol and methyl Carbitol. The solutionsuitable for the coating of magnet wire was made by dissolving the esterimide according to the procedure of Example 2. The temperature of themixing was adjusted to 180°-200° F. as the ethanol boiled above thistemperature.

Examples 6 and 7 illustrate the inability of two other glycol ethers,Cellosolve (2 ethoxy ethanol) and methyl Cellosolve (2-methoxy ethanol)to impart polymer solubility and stability.

EXAMPLE 6

353 grams of Cellosolve were used in place of the methyl Carbitol inExample 1 and the same procedure followed as in that Example. After thecollection of 500 cc of distillate and obtaining a temperature of 446°F. the reaction mixture was still cloudy. The theoretical amount ofwater available based on the charge was 238 cc. While still cloudy, thebatch gelled.

EXAMPLE 7

300 grams of methyl Cellosolve were used in place of methyl Carbitol inExample 1. Following the same procedure the reaction was still cloudyafter collecting 486 cc of distillate. Upon obtaining a sample viscosityof V 1/2 (Gardner-Holdt) at 30% in cresylic acid the batch gelled whilestill containing unreacted terephthalic acid.

EXAMPLE 8

    ______________________________________                                                       Grams                                                          ______________________________________                                        1. Neopentyl Glycol                                                                             73                                                          2. Ethylene Glycol                                                                             397                                                          3. THEIC         1075                                                         4. TMA           712                                                          5. MDA           367                                                          6. TA            811                                                          ______________________________________                                    

A polyester-imide was made with a hydroxyl/carboxyl ratio of 2/1.

Parts 1 through 5 were loaded into a 5-liter flask. The mixture washeated to 220° F. and 6 added. The batch was heated to 460° F. and afterobtaining 320 cc of distillate, the batch was clear and had a sampleviscosity of T (Gardner-Holdt) at 30% solids measured in cresylic acid.The distillation column was removed and 20 to 22 inches of vacuum wereapplied at 380° to 410° F. whereupon 34 cc of distillate were obtained.

EXAMPLE 9

The polyester-imide of Example 8 was dissolved in a methyl Carbitol andSolvesso 150 mixture using the procedure of Example 3.

The polyester-imide was soluble in the methyl Carbitol but upon additionof the hydrocarbon diluent it became cloudy and the N-methyl pyrrolidoneadded was needed to maintain clarity. Upon standing for several weeksthe wire enamel became cloudy in contrast to the polyester-imide intowhich the methyl Carbitol is coreacted.

    ______________________________________                                                            Grams                                                     ______________________________________                                        1.     Polyester-imide of Example 8                                                                     375                                                 2.     Methyl Carbitol    120                                                 3.     Solvesso 150       120                                                 4.     Mondur SH          32                                                  5.     Methyl Carbitol    48                                                  6.     TPT                8.5                                                 7.     Cresylic Acid      8.5                                                 8.     Methyl Carbitol    50                                                  9.     Solvesso 150       50                                                  10.    N-Methyl Pyrrolidone                                                                             60                                                  ______________________________________                                    

The resulting viscosity was a V at 45% solids.

EXAMPLE 10

This Example illustrates a polyester-imide useful as a wire coating whenapplied from solvent using conventional application techniques. It alsocan be applied as a hot melt using a heated applicator.

OH/COOH=1.81/1.0, 21.5% imide, 6.1% methyl Carbitol based on the totalequivalents charged, 10.5% of the hydroxyl equivalents present as methylCarbitol.

    ______________________________________                                                       Grams                                                          ______________________________________                                        1. Methyl Carbitol                                                                             212.8                                                        2. Ethylene Glycol                                                                             197.4                                                        3. THEIC         765                                                          4. TMA           493                                                          5. MDA           253                                                          6. Zinc Acetate  1.31                                                         7. DMT           655                                                          8. Xylene        150                                                          ______________________________________                                    

The above reactants were loaded into a flask equipped with a Snydercolumn, agitator and thermometer. The temperature was increased to 180°C. within two hours whereupon 72 cc of distillate were obtained. Thetemperature was allowed to increase to 210° C. Upon obtaining 342 cc ofdistillate the distillation under atmospheric conditions was complete. Avacuum was applied and 64 additional cc were obtained at a temperatureof 200° C. whereupon the distillation again ceased.

EXAMPLE 10-A

A wire enamel solution was made by dissolving 650 parts of thepolyester-imide made in Example 10 in 67 parts of methyl Carbitol and 77parts of Solvesso 150 at 120° C. At 60° C., 136.5 parts of a 40%solution of Mondur SH in methyl Carbitol was added followed by 14.3parts of TPT premixed with 10 parts of methyl Carbitol. The solution washeld at 125° C. for 3 hours and diluted with 52 parts of NMP and 218parts of a methyl Carbitol/Solvesso solids by volume. The propertieswhen coated and baked onto 18 gauge copper wire were good.

The stack loss of the wire enamel was determined with the aid of TiO₂.The average retention was found to be 91.97% resulting in a stack lossof 8.03% and effective solids of 46.26%. The stack losses of acommercial polyester-imide ISOMID® made without methyl Carbitol had anunexpectantly higher stack loss of 10.25%.

EXAMPLE 10-B

1250 parts of the polyester-imide made in Example 10 were crushed andloaded into a 3 liter flask. 37 parts of ethylene glycol were added andthe contents heated to 150° C. and melted with agitation. At 122° C.,300 parts of a 40% solution of Mondur SR in cresylic acid were addedalong with 87 parts of tetra phenyl titanate. The reaction was held at150° C. for 2 hours.

When applied onto copper wire in four passes using an applicator heatedto 180° C., a smooth coating was obtained with acceptable mechanicalproperties.

EXAMPLE 10-C

1000 parts of the polyester-imide made in Example 10 were processed andapplied to 18 gauge copper wire as in 10-B using 30 parts of ethyleneglycol, 240 parts of Mondur SH dissolved in methyl Carbitol and 70 partsof tetra phenyl titanate.

EXAMPLE 11

287 grams of butyl Carbitol were added in place of the methyl Carbitolin Example 10-A. The polyester-imide was processed as in Example 10 andthe resulting product compounded into a wire enamel using a 50:50 butylCarbitol/Solvesso 150 solvent blend (by volume). The wire enamel wascoated onto copper wire with good results. The viscosity was a U at 50%solids.

In place of the 50:50 butyl Carbitol/Solvesso 150 solvent blend therecan also be used 100% butyl Carbitol as the solvent to give a producthaving 50% solids.

EXAMPLE 12

237.5 grams of ethyl Carbitol were used in place of the methyl Carbitolin Example 10. The resulting product was compounded into a wire enamelas in Example 10-A using a 50:50 butyl Carbitol/Solvesso 150 solventblend in place of the methyl Carbitol/Solvesso and coated onto 18 gaugecopper wire. The viscosity was a Y at 50% solids.

In place of butyl Carbitol/Solvesso 150 there can be used 100% butylCarbitol as the solvent. Also there can be used a mixture of ethylCarbitol and butyl Carbitol as the solvent, e.g., 50:50 by volume.

EXAMPLE 13

    ______________________________________                                          Reactant            Batch Weight, Grams                                     ______________________________________                                        1.  Propasol Solvent DM                                                           (Dipropylene glycol monomethyl                                                ether)                262                                                 2.  Ethylene Glycol       197                                                 3.  Tris-2-(Hydroxyethyl) Isocyanurate                                                                  765                                                 4.  Trimellitic Anhydride 493                                                 5.  Methylene Dianiline   253                                                 6.  Zinc Acetate          1.31                                                7.  Dimethyl Terephthalate                                                                              655                                                 8.  Xylol                 150 ml.                                             ______________________________________                                    

Parts 1, 2, 3, 4, 5, 6 and 8 were charged into a three-liter reactionkettle equipped with a Snyder Column, Dean Stark, condenser, thermometerand agitator. The batch was heated to 120° C. whereupon part 7 wasloaded. Over a 2 hour period the temperature was increased to 185° C.The reaction mixture was then allowed to cool to 125° C. overnight andreheated to 200° C. the following day. The reaction was held for onehour at 200° C. then allowed to rise 10° C. to 210° C. in 1 hour afterwhich 270 cc of distillate were obtained. The batch was then vacuumstripped under 22 inches of mercury vacuum for 10 minutes, accompaniedby an additional 34 cc of distillate. The final viscosity measured incresylic acid was J-K (Gardner-Holdt) at 30 percent solids. The reactionmixture was insoluble at 30 percent solids in propasol solvent DM.However, it was soluble at 30 percent solids in methyl Carbitol with aviscosity of leas than A.

EXAMPLE 13-A

    ______________________________________                                          Reactant          Batch Weight, Grams                                       ______________________________________                                        1.  Polyester-Imide of Example 13                                                                     650                                                   2.  Methyl Carbitol     66.9                                                  3.  Solvesso 150        76.9                                                  4.  Mondur SH at 40 percent solids                                                in Methyl Carbitol  135.5                                                 5.  Tetra isopropyl Titanate                                                                          14.3                                                  6.  Methyl Carbitol     109                                                   7.  Solvesso 150        109                                                   8.  N-methyl-2-pyrrolidone                                                                            52                                                    ______________________________________                                    

Parts 1, 2, 3 were charged into a three-liter reaction kettle equippedwith an agitator, condensor and thermometer. The batch was heated until1 was dissolved at 140° C. The reaction mixture was then cooled to 60°C. where 4 and 5 were added. The mixture was then heated to 120° C. andheld for two hours. When the heat was turned off, 6 and 7 were added,the batch was then sampled for viscosity. This sample remained clear andhad a viscosity of Z2. The N-methyl-2-pyrrolidone (8) was then added.The viscosity of the batch was then determined to be X three-fourths onthe Gardner-Holdt scale at 50% solids.

This enamel coated 18 AWG copper wire at 45 FPM (feet per minute) withan appearance rating of 3. The average cut through temperature was 349°C. and there were heat shocks of 0, 40, 90, 100 at the 1, 2, 3 and 4times mandrels when tested for one half hour at 200° C. with a 20percent prestretch of the wire.

EXAMPLE 14

This Example is a class F polyester-imide resin utilizingtrimethylolpropane as the triol in place of glycerine. Again, methylCarbitol represents 10% of the total hydroxyl equivalents.

    ______________________________________                                                       Grams                                                          ______________________________________                                        1. Methyl Carbitol                                                                             187                                                          2. Ethylene Glycol                                                                             207                                                          3. TMP           327                                                          4. TMA           411                                                          5. MDA           212                                                          6. TA            234                                                          7. TA            234                                                          8. Dibutyl tin oxide                                                                           1.4                                                          ______________________________________                                    

Parts 1-5 and 8 were loaded into a flask equipped with a Synder column,Dean Stock trap, condenser, thermometer and agitator. Heat was added andat 230° F., part 6 was added. The heat was increased to 320° F. whenpart 7 was added. Distillate was already being obtained at this time.The temperature was allowed to increase over a 4 hour period to420°-440° F. where the temperature was held until the reaction went tocompletion. At completion, 180 cc of distillate was obtained. Theresulting resin was soft and pliable.

The above resin was then made into a wire enamel.

EXAMPLE 14-A

    ______________________________________                                                         Grams                                                        ______________________________________                                        1.      Polyester-imide resin                                                         made in                                                                       Example 14     375                                                    2.      Methyl Carbitol                                                                              120                                                    3.      Solvesso 150   120                                                    4.      Mondur SH      32                                                     5.      Methyl Carbitol                                                                              48                                                     6.      TPT            8.5                                                    7.      Methyl Carbitol                                                                              8.5                                                    8.      Ethylene Glycol                                                                              17                                                     ______________________________________                                    

Parts 1-3 were loaded to a flask equipped with condenser, thermometerand agitator. The heat was increased to 250° F. until the resindissolved. The heat was then removed and the mix allowed to cool. At220° F. part 4 predissolved in 5 was added. At 130°-140° F, part 6premixed with part 7 was added. Heat was then applied until thetemperature reached 250° F. where it was held for a period of 2 hours.At the end of the 2 hours, the ethylene glycol was added. The resultingmix had a viscosity of W- at 47.4% solids. When run at 45 ft/min on 18gauge copper wire, the runnability was a 3, the mandrel after snap was3X's, the abrasion resistance was 1225-1525 grams, the average cutthrough temperature was 308° C. Heat shocks of 0, 50, 60, 90% at 1, 2, 3and 3 X's mandrel were obtained, when tested at 175° C. for 1/2 hourswith a 20% prestretch of the wire.

EXAMPLE 15

This illustrates a Class F polyester-imide utilizing another glycolether in place of the methyl Carbitol. The glycol ether used was DowanolTPM(tripropylene glycol monomethyl ether). The Dowanol TPM comprised 10%of the total hydroxyl equivalent.

    ______________________________________                                                       Grams                                                          ______________________________________                                        1. Dowanol TPM   322                                                          2. Ethylene Glycol                                                                             207                                                          3. Glycerine     224                                                          4. TMA           411                                                          5. MDA           212                                                          6. TA            234                                                          7. TA            234                                                          8. Dibutyl tin oxide                                                                           1.4                                                          ______________________________________                                    

Parts 1-4 and 8 were loaded into a flask equipped with a Snyder column,Dean Stark trap, condenser, agitator and thermometer. Heat was added andat 230° F. part 5 was added. The procedure following the addition wasthe same as in Example 14. The resulting resin was soft and pliable andwas soluble in methyl Carbitol.

EXAMPLE 15-A

The resin of Example 15 was then made into wire enamel coating solution.

    ______________________________________                                                         Grams                                                        ______________________________________                                        1.      Polyester-imide resin                                                         made in                                                                       Example 15     375                                                    2.      Methyl Carbitol                                                                              120                                                    3.      Solvesso 150   120                                                    4.      Mondur SH      32                                                     5.      Methyl Carbitol                                                                              48                                                     6.      TPT            8.5                                                    7.      Methyl Carbitol                                                                              8.5                                                    8.      Ethylene Glycol                                                                              17                                                     ______________________________________                                    

The procedure for this enamel was identical to the one in Example 14.

The resulting enamel had a viscosity of V at 44.7% solids. It was coatedat 45 ft/min onto 18 gauge copper wire and had a runnability of 3, a2X's mandrel after snap, abrasion resistance of 1325-1466 grams and acut through temperature of 246° C.

EXAMPLE 16

This illustrates a polyester-imide where the difunctional glycol wascompletely deleted from the formula and where the methyl Carbitol was41% of the total hydroxyl equivalents.

    ______________________________________                                                          Grams                                                       ______________________________________                                        1. Methyl Carbitol  252                                                       2. THEIC            261                                                       3. TMA              384                                                       4. MDA              198                                                       5. TA               166                                                       6. Dibutyl tin oxide (catalyst)                                                                   .5                                                        ______________________________________                                    

Parts 1-4 and 6 were loaded into a flask equipped with a Snyder Column,Dean Stark trap, condenser, agitator and thermometer. Heat was appliedand the temperature allowed to rise over a 2 hour period to 330° F.,whereupon part 5 was added. The temperature increased over a 5 hourperiod to 460° F., by which time the batch had cleared and most of thedistillate was obtained. The batch was then allowed to cool overnight.The next day the temperature was again allowed to rise to 464° F. over a1 3/4 hour period at which time additional distillate could not beobtained. The total distillate obtained was 100 cc. The final productwas a clear hard resin soluble in methyl Carbitol and which had aviscosity of R-S measured at 30% solids in cresylic acid.

EXAMPLE 16-A

The resin of Example 16 was then processed into a wire enamel coatingsolution.

    ______________________________________                                                        Grams                                                         ______________________________________                                        1.       Polyester-imide                                                               resin of                                                                      Example 16   375                                                     2.       Methyl Carbitol                                                                            120                                                     3.       Solvesso 150 120                                                     4.       Mondur SH    32                                                      5.       Methyl Carbitol                                                                            48                                                      6.       TPT          8.5                                                     7.       Methyl Carbitol                                                                            8.5                                                     8.       Ethylene Glycol                                                                            17                                                      9.       Methyl Carbitol                                                                            50                                                      10.      Solvesso 150 50                                                      ______________________________________                                    

The procedure for this enamel was identical to that of Example 14A,except that this mix contained parts 9 and 10 which adjusted theviscosity to a Y 1/2 at 43.9% solids.

When run on 18 gauge copper wire at 45 ft/min, the enamel had arunnability of 3, a 1X's mandrel after snap, an abrasion resistance of1375-1483 grams, and a cut through temperature of 260° C.

EXAMPLE 17

    ______________________________________                                          Reactant           Batch Weight, Grams                                      ______________________________________                                        1. Phenyl Glycol Ethers*                                                                           132.5                                                    2. Ethylene Glycol   98.7                                                     3. Tris-(2-Hydroxy ethyl) isocyanurate                                                             382.5                                                    4. Trimellitic Anhydride                                                                           246.5                                                    5. Methylene Dianiline                                                                             126.5                                                    6. Zinc Acetate      .66                                                      7. Dimethyl Terephthalate                                                                          327.5                                                    8. Xylol             150                                                      ______________________________________                                         *Phenyl Glycol Ethers are a blend of 70 percent ethylene glycol monopheny     ether and 30 percent diethylene glycol monophenyl ether as obtained from      Union Carbide.                                                           

The reaction was carried out as described in Example 13 with a total of204 cc of distillate obtained. The final viscosity at 30 percent solidsin cresylic acid was P to O on the Gardner-Holdt scale. The same checkcut using methyl Carbitol as the solvent gave a viscosity of less thanA.

EXAMPLE 17-A

A wire enamel mix similar to Example 13-A was then prepared from theabove polyester-imide. The viscosity at 50 percent solids however was aZ1. Therefore 100 grams of additional solvent was added, 50 grams ofmethyl Carbitol and 50 grams of Solvesso 150. The final viscosity was Xone-fourth on the Gardner-Holdt scale at 48 percent solids.

EXAMPLE 18

This illustrates the use of methoxytriglycol (triethylene glycolmonomethyl ether) in place of methyl Carbitol. The methoxy triglycolrepresented 10% of the total hydroxyl equivalents.

    ______________________________________                                                       Grams                                                          ______________________________________                                        1. Methoxytriglycol                                                                            166                                                          2. Ethylene Glycol                                                                             135                                                          3. THEIC         414                                                          4. TMA           267                                                          5. MDA           138                                                          6. TA            152                                                          7. TA            152                                                          8. Dibutyl tin oxide                                                                           .9                                                           ______________________________________                                    

The procedure was the same as that of Example 4.

EXAMPLE 18-A

The resulting resin was then made into an enamel.

    ______________________________________                                                        Grams                                                         ______________________________________                                        1.       Polyester-imide                                                               resin of                                                                      Example 18   375                                                     2.       Methyl Carbitol                                                                            120                                                     3.       Solvesso 150 120                                                     4.       Mondur SH    32                                                      5.       Methyl Carbitol                                                                            48                                                      6.       TPT          8.5                                                     7.       Methyl Carbitol                                                                            8.5                                                     8.       Ethylene Glycol                                                                            14                                                      ______________________________________                                    

The procedure for this enamel was the same as that of Example 14-A. Thefinished enamel had a viscosity of Y- at 49.3% solids.

The percent solids of the wire enamel solutions were determined usingtwo gram samples in a forced air oven held at 200° C. for two hours. Thecut through values in the present invention were determined using a 2000gram weight. These conditions are more stringent than using a 600 gramweight as in the aforementioned Okada Japanese published application.

The heat shock testing at 175° C. and 200° C. is also more severe thanthe testing at 150° C. as in Okada.

One of the advantages of being able to make higher solids wire enamelsmakes it possible to reduce the number of passes required to build upthe thickness of the coating on the wire.

The glycol ether modified polyester-imides of the present invention arealso useful in hot melt application to the wire, e.g., at 85-88% usingmethyl Carbitol or cresylic acid.

The compositions can comprise, consist essentially of or consist of thematerials set forth.

The following table shows the properties with 18 gauge copper wirecoated with the compositions of some of the examples described above.

    __________________________________________________________________________         Wire       Mandrel                                                                            Cut                                                           Speed      After                                                                              THrough                                                  Example                                                                            Ft/min                                                                            Appearance                                                                           Snap ° C                                                                         1X 2X 3X 4X                                         __________________________________________________________________________    2    45  3      1X   360  80*                                                                              100                                                                              100                                                                              100                                        3    45  3      1X   366   0*                                                                              20  90                                                                              100                                        4    45  3      1X   355  10*                                                                              40  70                                                                              100                                        5    40  3      2X   364  20*                                                                              80 100                                                                              100                                        9    45  3      1X   341  50*                                                                              80 100                                                                              100                                        10-A 45  3      2X   366  10*                                                                              60 100                                                                              100                                        10-B 40  3      2X   350  20*                                                                              90  90                                                                              100                                             45  2-3    1X   358  10*                                                                              80  90                                                                              100                                        10-C 40  3      2X   348  50*                                                                              90 100                                                                              100                                             45  2-3    1X   348  60*                                                                              80  90                                                                               90                                        11   45  3      3X   350  40**                                                                             80 100                                                                              100                                        12   45  3      2X   352  20**                                                                             80 100                                                                              100                                        17-A 45  2      1X   359  60**                                                                             90 100                                                                              100                                        18-A 45  3      1X   351  30**                                                                             90 100                                                                              100                                        __________________________________________________________________________     *Heat shock tested at 200° C for 1/2 hour at 20% prestretch            (percent pass)                                                                **Heat shock tested at 175° C for 1/2 hour at 20% prestretch           (percent pass)                                                           

In the claims when reference is made to the reaction product ofterephthalic acid or isophthalic acid, it should be understood that theterm is intended to cover the product whether the carboxylic acidcomponent is added as the free acid or as an ester thereof, e.g.,dimethyl terephthalate, which splits off an alcohol in the reaction.When the term "free acid" is used in the claims, then the term islimited to reacting the acid as such, e.g., terephthalic acid, and doesnot cover the use of the esters, e.g., dimetyl terephthalate.

The polyester-polyimide can be used not only as an insulating coatingfor wires but also to coat electrical conductors in other forms, e.g.,sheet metal such as copper, silver or aluminum sheets.

What is claimed is:
 1. A solution in a solvent comprising at least 40%of a glycol ether which is a monoalkyl ether of diethylene glycol having1 to 4 carbon atoms, phenoxy ethanol or the monophenyl ether of ethyleneglycol of a polyester-polyimide having a hydroxy to carboxyl ratio of1.25:1 to 2:1, 96 to 50% ester groups, 5 to 50% imide groups, thepolyimide being an imide of reactants comprising an aromatic diamine andtrimellitic anhydride, the polyester being an ester of isophthalic acidor terephthalic acid or benzophenone dicarboxylic acid with up to 10% ofan alkane dicarboxylic acid having 6 to 10 carbon atoms with alcoholswherein 5 to 45% of the hydroxyl groups are contributed by (I) anetheralcohol which either (a) has the formula

    RO(C.sub.n H.sub.2n O).sub.x H

where R is an alkyl group of 1 to 4 carbon atoms or phenyl, n is 2 or 3and x is 2 or 3 or (b) is the monophenyl ether of ethylene glycol, (II)at least 20% of the hydroxyl group are contributed by a trihydricalcohol which is tris(2-hydroxyethyl)cyanurate, glycerine,trimethylolpropane or trimethylolethane and (III) any balance ofhydroxyl groups are contributed by a dihydric alcohol, saidpolyester-polyimide having a sufficiently low molecular weight that itis soluble in said solvent.
 2. A solution in a solvent comprising atleast 40% of a glycol ether which is a monoalkyl ether of diethyleneglycol having 1 to 4 carbon atoms, phenoxyethanol or the monophenylether of diethylene glycol of a polyester-polyimide having a hydroxy tocarboxyl ratio of 1.25:1 to 2:1, 95 to 50% ester groups, 5 to 50% imidegroups, the polyimide being an imide of reactants comprising a diamineand trimetallitic anhydride, the polyester being an ester of isophthalicacid or terephthalic acid or benzophenone dicarboxylic acid with up to10% of an alkane dicarboxylic acid having 6 to 10 carbon atoms withalcohols wherein 5 to 45% of the hydroxyl groups are contributed by (I)an ether-alcohol which either (a) has the formula

    RO(C.sub.n H.sub.2n O).sub.x H

where R is an alkyl group of 1 to 6 carbon atoms or phenyl, n is 2 or 3and x is 2 or 3 or (b) is the monophenyl ether of ethylene glycol, (II)at least 20% of the hydroxyl group are contributed by a trihydricalcohol and (III) any balance of hydroxyl groups are contributed by adihydric alcohol, said polyester-polyimide having a sufficiently lowmolecular weight that it is soluble in a mono lower alkyl ether ofdiethylene glycol or in the monophenyl ether of diethylene glycol orphenoxyethanol or a mixture of said phenyl ethers.
 3. A solutionaccording to claim 1 wherein (II) contributes at least 30% of thehydroxyl groups and the hydroxy to carboxyl ratio is 1.8:1 to 2:1.
 4. Asolution according to claim 1 wherein the solvent is at least 50% ofsaid glycol ether.
 5. A solution according to claim 4 wherein thesolvent is 100% of said glycol ether, said monoalkyl ether having 1 to 2carbon atoms in the alkyl group.
 6. A solution according to claim 1wherein the solvent is a mixture consisting essentially of said glycolether and a hydrocarbon.
 7. A solution according to claim 6 wherein thehydrocarbon is an aromatic hydrocarbon.
 8. A solution according to claim1 wherein the solvent includes at least 40% of a mixture ofphenoxyethanol and phenoxyethoxyethanol and (I) is a mixture ofphenoxyethanol and phenoxyethoxyethanol.
 9. A solution according toclaim 1 wherein the solvent includes at least 40% of a mono 1 to 4carbon atom alkyl ether of diethylene glycol.
 10. A solution accordingto claim 9 containing at least 30% of said polyester-polyimide wherein Ris butyl and (I) is (a) and the glycol ether consists ofbutoxyethoxyethanol.
 11. A solution according to claim 10 containing 45to 55% of said polyester-polyimide.
 12. A solution according to claim 9wherein the solvent includes at least 40% of methoxyethoxyethanol andthe solution contains at least 30% of said polyester-polyimide.
 13. Asolution according to claim 12 wherein the sole glycol ether present asa solvent is methoxyethoxyethanol.
 14. A solution according to claim 12wherein the glycol ether is a mixture of methoxyethoxyethanol andethoxyethoxyethanol.
 15. A solution according to claim 14 wherein R isethyl and (I) is (a).
 16. A solution according to claim 12 wherein R ismethyl and (I) is (a).
 17. A solution according to claim 16 containing45 to 55% of said polyester-polyimide.
 18. A solution according to claim1 wherein any dihydric alcohol present is an alkane diol having 2 to 8carbon atoms.
 19. A solution according to claim 18 wherein the diamineis methylene dianiline, tolylene diamine or oxydianiline.
 20. A solutionaccording to claim 19 wherein the diamine is methylene dianiline, thedicarboxylic acid is terephthalic acid.
 21. A solution according toclaim 20 wherein the polyester-polyimide has a molecular weight of 550to
 1200. 22. A solution according to claim 20 wherein (I) ismethoxyethoxyethanol, ethoxyethoxyethanol, butoxyethoxyethanol,methoxypropoxypropanol, methoxypropoxypropoxypropanol, phenoxyethanol orphenoxyethoxyethanol.
 23. A solution according to claim 22 wherein thetrihydric alcohol is tris(2-hydroxyethyl) isocyanurate.
 24. A solutionaccording to claim 23 which has no component (III) in thepolyester-polyimide.
 25. A solution according to claim 23 whereincomponent (III) is present in the polyester-polyimide in an amount of atleast 10% and is ethylene glycol.
 26. A solution according to claim 22wherein the tihydric alcohol in the polyester-polyimide is glycerine ortrimethylol propane.
 27. A solution according to claim 22 wherein (I) ismethoxyethoxyethanol.
 28. A solution according to claim 27 wherein 5 to30% of the hydroxyl groups are contributed by (I).
 29. A solutionaccording to claim 28 wherein 5 to 12% of the hydroxyl groups arecontributed by (I).
 30. A solution according to claim 19 wherein 5 to30% of the hydroxyl groups are contributed by (I).